Dishwasher appliances generally include one or more pumps, such as a wash pump or drain pump. The wash pump can circulate liquid throughout a wash chamber of the dishwasher, for washing or rinsing items contained therein. The drain pump can remove liquid from the wash chamber of the appliance. For example, liquid can collect in a sump disposed at a bottom of the wash chamber during operation of the dishwasher appliance and the drain pump can be operated to urge such liquid from the sump to a drain where the liquid can flow out of the appliance.
However, both the wash pump and the drain pump can experience cavitation or can enter into a dry state. For example, when the wash pump is not fully primed with liquid it will experience cavitation, thus intermittently experiencing both wet states and dry states. Likewise, when the drain pump has successfully drained all of the liquid from the sump, it will enter a dry state.
Operation of a pump while experiencing cavitation or during a dry state can result in several distinct problems. One problem includes the creation of undesirable noise. In particular, operation of a pump during cavitation or in a dry state can create much louder noise than operation of the pump in a wet state. Increased noise can reduce user satisfaction. Further, increased noise above certain levels can cause a dishwasher to be non-compliant with regulations governing appliance sound levels.
Another problem caused by operation of a pump during cavitation or a dry state is that it results in the unnecessary use of energy. In particular, appliance energy consumption should be minimized to keep energy costs low and to meet regulatory requirements or other certification standards. Thus, such unnecessary use of energy should be eliminated.
Yet another problem is that operation of a pump during cavitation or a dry state may cause pitting or other damage to the pump itself or to other system components.
In particular, certain dishwashers can also include one or more heating elements which serve to heat the wash water. Operation of the heating elements while the wash pump is in a dry state (i.e. wash water is not circulating through the system) can be dangerous to both the dishwasher integrity and to user safety. For example, if energized in the absence of water to heat, the heating elements can potentially overheat and catch fire, a potentially disastrous situation. As another example, a non-resettable fuse can protect the heating elements from overheating. When the non-resettable fuse blows, the user can be required to place a service call, costing both time and money.
Previous attempts at solving the above noted problems have failed or are undesirable for particular reasons. For example, dishwasher drain heights can vary from one model to another or can be constrained at installation. Therefore, it can be difficult to finely tune drain pump operation time based on physical drain characteristics. As another example, attempts to minimize drain pump dry state operation by simply reducing total drain time can result in air lock, failure to fully drain, or other undesirable results.
Thus, improved systems and methods for detecting dishwasher pump cavitation and dry state are desired.